Turbochargers in internal combustion engines are subject to high centrifugal forces due to high rotational speeds. These forces lead to correspondingly high loads on the material of the turbine wheel and of the compressor wheel of the exhaust turbocharger. These loads can lead to damage to the rotating components and therefore to failure of the exhaust turbocharger. To determine that the load limit has nearly been reached and to avoid damage, it is provided, in accordance with European Published Patent Application No. 0 491 275, for the ratio of boost pressure to induction pressure in the induction tract of the internal combustion engine to be monitored and compared with a predetermined minimum ratio, an alarm signal being generated if the actual ratio is lower than the minimum ratio. The minimum ratio characterizes a minimum boost pressure which is to be achieved under the current conditions of the internal combustion engine as a function of the induction pressure. If this minimum pressure is not achieved, there are critical operating conditions, whereupon the warning signal is generated, in order to alert the driver to the malfunction.
The appliance and method described in European Published Patent Application No. 0 491 275 have the drawback that a warning signal is only generated when the boost pressure which is to be generated is no longer achieved and therefore correct operation cannot be ensured. Furthermore, there is a risk that by this time material has already been damaged as a result of an excessively high load, and during further operation this damage can lead to complete failure of the charger.
It is an object of the present invention to avoid damage in exhaust turbochargers as a result of high material loads and indicating unacceptably high loads at an early stage.